This invention is related to metal working machinery and processes, and more particularly, to improvements in an apparatus for the, as well as the process of, continuous roll casting of ferrous and non-ferrous metals. In this regard, Sir Henry Bessemer first conceived the concept of continuous roll metal casting in the year 1853. Since then there have been a number of developments in continuous roll metal casting technology.
One such area of development pertains to a hot rolling casting process. In the hot rolling casting process, molten metal is fed into the bite between a pair of counter-rotating cooled rolls wherein solidification is initiated when the metal contacts the rolls. Solidification prior to the roll nip, or point of minimum clearance between the rolls, causes the metal to be deformed, or hot rolled, prior to exiting the rolls as a solidified sheet.
While the hot rolling casting process has provided a number of benefits, there remains a desire to improve upon such a process in a number of ways. One such area of improvement concerns the number of steps that have been necessary to produce a steel coil using the hot rolling casting method. Heretofore, the typical hot rolling process comprised the steps of: (1) casting of the molten metal, (2) hot rolling the cast material into sheet, (3) pickling the hot rolled sheet so as to remove surface skin, (4) cold rolling the pickled sheet, (5) cleaning the cold rolled sheet, (6) annealing the cleaned cold rolled sheet and, (7) remove shape defects of the rolled sheet. As can be appreciated, each process step adds an expense to the overall cost of production. Hence, it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would not need as many steps as heretofore required with known twin roll casting process. More specifically, it would be highly desirable to provide such an improved apparatus and process that eliminates the steps of cold rolling, cleaning and annealing.
Another area of improvement concerns the ability to produce a cast metal strip that exits the casting rolls wherein the cast metal strip exhibits a consistent and predetermined thickness. It would thus be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would produce a cast metal strip exiting the casting rolls that exhibits a consistent and predetermined thickness.
In the hot rolling casting process it is important to provide an apparatus, as well as a process, that results in the least number of (or essentially completely eliminates the) physical defects in the hot rolled strip. After the hot rolled strip has been pickled and the skin removed and the skin passed so as to provide a cold rolled-like finish, the roll is being wound around a precision mandrel and simultaneously submitted to reversed bends as to elongate 80% of the grain of the steel. The Precision (deflection free) mandrel then detects the part of the strip with shorter grains and elongate the shorter grain portion of the strip so that all grains are of equal lengths. During the winding process, the metal strip is subjected to high tension as well as being simultaneously subjected to reverse bends. Any defects in the strip while being subjected to this process can result in certain undesirable conditions. Thus, it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would produce a metal strip that exhibits a consistent thickness and shape.
For example, if there is any non-uniformity in the strip thickness or unequal length in the grains of the strip as the material is being subjected to reverse bending to a predetermined amount and then wound around the mandrel, tension forces are exerted on the strip. If the magnitude of the tension forces on the strip exceeds the yield strength of the material of the strip as it is being subjected to the reverse bends, then the shorter grains of the strip will elongate to the same length as all the other grains, and this will result in a strip that is free of defects. It can thus be appreciated that it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would monitor and control the elongation of the strip so that the entire cross section of the strip is elongated by a given preset amount thereby eliminating all shape defects wherein the strip does not exhibit defective conditions.
Another example of defects heretofore found in strip steel is edge waves. More specifically, this edge wave condition is caused because the grains on the edges of the strip are longer (or thinner) than the grains on the center of the strip so that the grains in the center of the strip are thicker. As the material is wound about the precision drum and simultaneously being subjected to reverse bends so that the built-up of the layers causes the tension on the thicker part of the strip (i.e., the center of the strip) to be higher than the tension on the thinner part of the strip (i.e., the edge portions).
Keeping in mind that the tension is assisted by the reverse bending rolls, as the winding process continues the tension on the thicker strip becomes greater than what the entire cross section of the strip can withstand so that the thicker part of the cross section elongates the short grains, as it tries to travel at a higher peripheral speed than the thinner part, is first elongated and then the elongation extends toward the edges of the strip until the total cross section of the strip is elongated and monitored to insure that all grains are of equal length. It can thus be appreciated that it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would monitor and control the elongation of the strip so as to essentially eliminate the condition of edge waves.
As still another example of defects heretofore found in steel strip there is the condition known as center buckle or oil can or cross bow. These defects are caused because the grains on the middle part of the strip are longer (thinner) than the grains on the edges of the strip (thicker). As the material is subjected to reverse bends so that 80% of the cross section of the grains are elongated and then wound about the precision drum, the shorter grains are subjected to higher tension and are elongated so that all grains are of equal length.
Keeping in mind the assistance provided by the reverse bending rolls, the tension on the strip is greater than what the entire cross section of the strip can withstand, the thicker part of the cross section, as it tries to travel at a higher peripheral speed than the thinner part, is first elongated and then the elongation extends, beginning at the edges of the strip and then moving toward the center of the strip, until the total cross section of the strip is elongated. It can thus be appreciated that it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would monitor and control the elongation of the strip so as to essentially eliminate the condition of center buckle or oil can or cross bow.
As yet another example of defects heretofore known in steel strip is the condition known as camber. The condition of camber is caused because the grains of one edge of the strip is longer (thinner) than the grains of the opposite edge of the strip. The edge of the strip where the grains are shorter (thicker), as the material is wound about the precision drum, the built-up of the layers causes the tension on the side of the shorter grains of the strip to be higher than the tension on the longer edge of the strip.
Keeping in mind the assistance provided by the reverse bending rolls, the shorter (thicker) edge of the strip is elongated first. Then the elongation of the strip, progressively move from the thicker to the thinner edge of the strip until the entire cross section of the strip is elongated a predetermined amount. It can thus be appreciated that it would be highly desirable to provide an improved apparatus and process for the continuous roll casting of metals that would monitor and control the elongation of the strip so as to essentially eliminate the condition of camber.